Phosphocalcic cement - Bone graft - Bone filling
Graftys® BCP
Graftys BCP Dental
Resorbable Bioactive Cement
Calcium phosphate cements
The calcium phosphate cements (CPC) are hydraulic cements, their setting is obtained by an acid-base or hydrolysis reaction between a powder and a liquid. After mixing, a calcium phosphate of intermediate alkalinity precipitates.
Principle of obtaining calcium phosphate cements
A cement material consists of a solid powder phase which initially forms a plastic paste by mixing with a liquid phase. This viscous paste will transform into a stiff paste during setting, increasing its mechanical strength progressively up to saturation (hardening).
Biological properties
Calcium phosphate cements are highly biocompatible and osteoconductors. Their excellent biocompatibility and their formation at low temperature allow the incorporation of the organic molecules and also of the living cells. Moreover they are used like materials candidate for tissue engineering, and like alternative to conventional porous ceramics.
Two types of resorption might be distinguished, passive and active. The passive resorption is due to the rate of dissolution of material in the biological fluids and it depends on the final components of cement. This type of resorption is determined by the porosity of the samples, ionic substitutions, the crystallinity and the pH of the tissue-cement interface.
The active resorption is mediated by cellular activity (osteoclasts and
macrophages). The activity of osteoclasts produces a pH of 5,5 which increases
the dissolution of the implant. Usually this type of resorption occurs only
on the surface of cement because the pores present in cements do not allow
the penetration of the cells or the blood vessels into the core of material.
This is the big drawback of calcium phosphate cements which reabsorb slowly
because of the lack of macroporosity.
The clinical applications
Brown and Chow envisaged the following applications for this type of materials in the field of orthopaedy:
Fixation of endoprosthesis
Filling of bone tumours
Field of dentistry and oral surgery
Covering the cavity to protect pulp or to cover exposed pulp
To replace or support the regeneration of lost bone because of the parodontal disease
Alveolar filling
Fixation of the oral implants
In short, we can say that calcium phosphate cements offer the advantage of being injectable, mouldable and to adapt to the bone defects. Also they offer an excellent biocompatibility and are osteoconducturs. But, they have some problems concerning the reproducibility of their setting times, mechanical properties and their final biological properties.
Indeed, long setting times of calcium phosphate cements make their clinical applications very delicate. The resorption in vivo is very slow because of the lack of macroporosity and/or the pores present in cements do not allow the colonization of the cells or the blood vessels.
To overcome these deficiencies, several investigations were carried out: they proceeded to the technique of emulsion of calcium phosphates, they tried out the mixture of CPC with soluble and nontoxic crystals such as sugar or the mannitol; these crystals after hardening of material soaked in water are eliminated to leave place to pores
Another method was used to create macropores in the material by adding NaHCO3 in the starting powder. All these techniques did not improve the macroporosity of the CPC and the compressive strength remained very weak making these cements not applicable for load bearing applications.
To improve the mechanical properties and the macroporosity of the CPC, other techniques were employed: crystals of mannitol were reinforced by aramine fibres in the CPC. Studies showed the improvement of resistance thanks to the incorporation of the very soluble mannitol with chitosan in the CPC
These last techniques even if they have the merit to improve the properties of the CPC, carried out by incorporation of elements of foreign nature to the basic composition of cements making their synthesis difficult.
In order to contribute the optimization of the above mentioned properties, GRAFTYS proposes a new calcium phosphate biomaterial type cement integrating rapid resorbable phases with controlled dissolution in order to induce macroporosity within the calcium phosphate matrix. Once implanted in a bone defect, the hardened product has to be quickly resorbed by the cellular activity and biological fluids in order to allow bone colonization of the macropores.
The Graftys’s calcium phosphate cement patented in August 2006, have inherent qualities in this technology :
- Mouldability, Injectability
- Complete filling of a cavity
- Good apposition biomaterial-surrounding tissue
- Similarity with bone mineral phase
- Appropriate and lasting mechanical strength
- No exothermic effects during setting
- Non volume contraction or shrinkage during setting.
…While bringing two major innovations :
A calcium phosphate matrix for a rapid resorption
A macroporosity of high quality
Phosphocalcic cement - Bone graft - Bone filling
GRAFTYS - Eiffel Park - Bâtiment D - 415, rue Claude Nicolas Ledoux
Pôle d'Activités d'Aix en Provence - 13 854 AIX EN PROVENCE Cedex 3
Tel : + 33 (0)4 42 60 30 00 - Fax : + 33 (0)4 42 60 30 11